1. Field of the Invention
This invention relates to a chopper-folding mechanism for use in a rotary printing press, and more particularly to an apparatus for restraining the movement of a paper sheet during conveyance thereof along a paper sheet conveying path so as to apply a chopper-fold to the paper sheet.
2. Description of the prior art
A number of apparatuses for preventing both edges of a paper sheet from rising suddenly when it is subjected to a chopper-fold in a rotary printing press have heretofore been developed. These conventional apparatuses are disclosed, for example, in Japanese Laid-Open Utility Model Applications Nos. SHO58-127050, SHO 61-176152, SHO 62-17673, SHO 63-24169 and HEI 1-11163, and Japanese Laid-Open Patent Applications Nos. SHO 62-136478 and SHO 62-290680.
Out of these conventional apparatuses, those disclosed in the Japanese Laid-Open Utility Model Applications Nos. SHO 58-127050, SHO 61-176152 and SHO 63-24169 are constructed such that paper sheet guide members each having a suitable shape for restraining the movement of a paper sheet to be subjected to a chopper-fold are fixedly secured to a frame or the like above a paper sheet conveying path and adjacent to a folding slot (which is referred to as "first construction" hereinafter).
While, other conventional apparatuses disclosed in the Japanese Laid-Open Utility Model Application No. HEI 1-111663 and the Japanese Laid-Open Patent Applications Nos. SHO 62-136478 and SHO 62-290680 are each constructed such that a brush is mounted adjacent to a folding-slot so that the lower end thereof may slidably contact the upper surface of a paper sheet to be folded, and a stopper for stopping the movement of the paper sheet is mounted separately from the brush and in the paper sheet conveying path, each of the brush and the stopper having an independent shifting or displacement mechanism for changing their positions(which is referred to as "second construction" hereinafter).
Further, a further conventional apparatus disclosed in the Japanese Laid-Open Utility Model Application No. SHO 62-17673 is constructed such that a pair of endless belts are provided adjacent to a folding-slot formed in a paper sheet guide plate, and adapted to be driven by a driver means so as to run rotatably in a paper sheet conveying direction (which is referred to as "third construction" hereinafter).
Whereas, the above-mentioned prior art constructions have respective problems to be solved which will be mentioned below.
In the first construction, since the paper sheet guide members are fixedly secured to the frame, if during folding of the paper web underneath of the guide members or the folding-slot is jammed with a paper sheet, then the guide members hinder removal of the jammed paper sheet therefrom to put the apparatus into normal working condition. It is therefore necessary to detach and attach the paper sheet guide members before and after the restoring operation, thus lowering the operational efficiency.
Whilst, in the second construction, since the brush and the stopper have independent displacement or shifting mechanisms for changing their positions, if and when the above-mentioned jamming with a paper sheet occurs, then the brush and the stopper can be retracted quickly from their operating positions for the chopper-folding to their inoperative positions which do not interfere with the restoring operation, so that the restoring operation can be commenced immediately. However, the displacement mechanism of the brush and the stopper are each comprised of a lot of parts and relatively complex in structure so that manufacturing cost and maintenance cost thereof are both expensive. In addition, in case a change-over is made from a non-chopper-folding condition to a chopper-folding condition or vice versa, both the brush and the stopper have to be shifted separately. Therefore, failure of either one of the brush and stopper shifting operations results in an improperly folded paper sheet which has to be disposed of as waste.
Further, in the third structure, since the endless belts have flexibility and resilience, if jamming with a paper sheet occurs, restoring operation can be carried out while putting the belts aside along the paper sheet conveying path. However, since provision of a belt stretching mechanism and a belt driving mechanism in a relatively narrow space is required, difficulties are encountered when effecting assembly and maintenance thereof, and also manufacturing costs thereof are comparatively expensive.